Anna Barbauld was raised in the religious and intellectual tradition of Presbyterian Dissent, in which Unitarianism developed. Unitarians, or Socinians (from the name of the Italian religious thinker Faustus Sozzini), are known for their rejection of the notion of the Trinity in favour of a single-person Deity. A creed whose origins come from seventeenth-century Europe, in the eighteenth century the two distinguishing features of the English Unitarians were their belief in a Divine Creator from an argument from Design and the fact that they did not subscribe to the Thirty-Nine Articles of the Anglican Establishment. The Test Act (1673) meant that they could not hold state offices or attend university; this outsider status encouraged them to develop "an alternative, radical culture, strongly influenced by the ideas of the European Enlightenment, with an emphasis on the physical sciences, experiment and political reform" (Holmes 96). The first English Unitarian chapel was opened in 1774 by Theophilus Lindsay, and by 1800 there were approximately two hundred Unitarian chapels scattered throughout England. By 1768 one of its major proponents, Joseph Priestley, had "come to see Christ as no more than a unique man, a position much more radical than that of the earlier Unitarians" ( Yolton 533). In its recourse to reason, Unitarianism may be seen as "one of the numerous Enlightenment ways of elaborating a rational critique of religious orthodoxy" (Yolton 533). Such convictions influenced their support of repeal of the Test Acts, freedom of the press, abolition of the slave trade, and parliamentary reform, all subjects on which Barbauld wrote.

They established societies and reading groups, the most famous of which was the Lunar Society of Birmingham, whose members included James Watt, Erasmus Darwin, Thomas and Josiah Wedgwood, Joseph Priestley, and Thomas Beddoes. Individual congregations invited lay preachers like Samuel Taylor Coleridge to speak to them on public issues; William Hazlitt wrote a vivid account of Coleridge coming to preach at his father's Unitarian church at Wem near Shrewsbury in "My First Acquaintance with Poets." Their interest in encouraging public discussion meant that Unitarians owned newspapers, journals, and publishing houses and ran distinguished academies for higher education like the Warrington Academy. As Richard Holmes suggests, they "regarded themselves, with some justice, as the progressive intellectual elite of the nation" (96).

(Sources: Richard Holmes, Coleridge: Early Visions [1989] and John W. Yolton, ed. The Blackwell Companion to the Enlightenment [1991]).